01 Learning and memory Domina Petric, MD

http://factmyth.com/factoids/there-are-different-types-of-memory/

fMRI, PET fMRI (functional magnetic resonance imaging) and PET (positron emission tomography): discovering areas of the brain that are active during specific brain tasks. 

Learning Learning involves changes in the strength of synaptic connections between neurons. 

Long vs. short-term memories Long-term memories involve changes in protein synthesis and gene regulation and short-term memories do not.  Long-term memories in many cases involve structural modifications. 

Long term potentiation Long-term potentiation (LTP) is an enduring form of synaptic plasticity. It might be involved in many examples of declarative memory. It is present in the hippocampus. Hippocampus is involved in declarative memories. 

I. Short term memory

Sensory memory It is the shortest-term element of memory. It is the ability to retain impressions of sensory information after the original stimuli have ended. It acts as a kind of buffer for stimuli received through the five senses: sight, hearing, smell, taste and touch.

Sensory memory After the information is perceived, it is stored in sensory memory automatically and unbidden. The sensory memory can not be prolonged via rehearsal.

Sensory memory Sensory memory is an ultra short-term memory and decays or degrades very quickly (200 - 500 milliseconds) after the perception of an item.

Types of sensory memory The sensory memory for visual stimuli is the iconic memory. The memory for aural stimuli is known as the echoic memory. The memory for touch is the haptic memory. 

Smell Smell may be even more closely linked to other memories than the other senses. The olfactory bulb and olfactory cortex are physically very close (2 or 3 synapses away) to the hippocampus and amygdala (memory processes). 

Working memory The ability to remember and process information at the same time. It holds a small amount of information (around 7 items or less) in mind in an active, readily-available state for a short period of time (from 10 to 15 seconds, or sometimes up to a minute).

Transfer to long-term memory This information will quickly disappear forever unless we make a conscious effort to retain it. The short-term memory is a necessary step toward the next stage of retention. 

meaning and association Transfer mechanisms mental repetition meaning and association motivation 

Anatomy The central executive part of the prefrontal cortex at the front of the brain plays a fundamental role in short-term and working memory.

Neural loops of central executive control For visual data: activates areas near the visual cortex of the brain. For language: the ˝phonological loop˝ uses Broca's area.

II. Long term memory

02 Declarative memory The declarative memory system is the memory system that has a conscious component and it includes the memories of facts and events. 

Non declarative memory 04 Non declarative memory Non declarative memory (implicit memory) includes the types of memory systems that do not have a conscious component. 

Non declarative memory includes: memories for skills and habits (riding a bicycle, driving a car, playing piano) priming phenomenon simple forms of associative learning (classical conditioning or Pavlovian conditioning) simple forms of nonassociative learning (habituation and sensitization) 

Priming phenomenon It is a non conscious form of human memory concerned with perceptual identification of words and objects. It refers to activating particular representations or associations in memory just before carrying out an action or task.

Declarative memory: knowing what! Conclusion Declarative memory: knowing what! Nondeclarative memory: knowing how!

Anatomy of declarative memory The medial temporal lobe memory system is for declarative memory. It is composed of the hippocampus, the perirhinal, entorhinal and parahippocampal cortices.

F. D. Raslau, I. T. Mark, A. P. Klein, J. L. Ulmer, V. Mathews, L. P F.D.Raslau, I.T.Mark, A.P.Klein, J.L.Ulmer, V.Mathews, L.P.Mark. Memory Part 2: The Role of the Medial Temporal Lobe. American Journal of Neuroradiology. November 2014.

Medial temporal lobe Has hierarchic format in which information is: initially collected through the perirhinal and parahippocampal cortices than passes to the entorhinal cortex ultimately reaches the hippocampus

Exteroceptive information Exteroceptive (external to the organism) information is processed by the parahippocampal gyrus via the ventral and dorsal streams.

Ventral and dorsal stream The ventral stream from the occipital lobe consists of visual information (object recognition). The dorsal stream from the parietal lobe carries spatial context information to the parahippocampal gyrus.

Interoceptive information Interoceptive (internal to the organism) signals carry informations such as emotions and motivation. Interoceptive signals go from the medial prefrontal cortex, nucleus accumbens and amygdala. Then project to the rostral hippocampal formation and rhinal cortex regions.

The entorhinal cortex The medial entorhinal cortex (Brodmann area 28b) is actively involved in the processing of spatial information from the dorsal stream. The lateral entorhinal cortex (Brodmann area 28a) is actively involved in the object recognition information from the ventral stream.

http://www.brain-maps.com/gehirn/brodmann_areale.jpg

The rhinal cortex The rhinal cortex functionally differentiates familiar and novel information input: more familiar items are given fewer resources for encoding compared with new items a gatekeeper of the declarative memory system optimising memory encoding resources to novel information

Anterior temporal system perirhinal cortex temporopolar cortex lateral orbital frontal cortex amygdala

Anterior temporal system The anterior system is more involved in object and face recognition, conceptual identity and salience.

Semantic dementia Semantic dementia involves more of the anterior temporal system. Patients often show the deficits in fine grain object recognition.

Posterior temporal system parahippocampal cortex retrosplenial cortex (Brodmann areas 29 and 30) anterior thalamic nuclei mammillary bodies presubiculum and parasubiculum default network

Default network retrosplenial cortex posterior cingulate gyrus precuneus angular gyrus ventral medial prefrontal cortex

Posterior temporal system The posterior system is involved in scene recognition, location, trajectory, temporal context and order, and finally situations.

Alzheimer´s disease Alzheimer´s disease often involves more of the posterior temporal system and is frequently associated with deficits in scene discrimination.

The parahipoccampal cortex It is part of a larger network that connects regions of the frontal, parietal and temporal lobes.

The parahipoccampal cortex auditory association areas of the superior temporal gyrus polymodal association areas (the retrosplenial cortex, lateral inferior parietal lobule, dorsal bank of the superior temporal sulcus) temporal pole perirhinal cortex parahippocampal cortex entorhinal cortex medial prefrontal cortex dorsal lateral prefrontal cortex orbital prefrontal cortex insula

The parahipoccampal cortex Main function is facilitating contextual associations.

Anatomy of procedural (implicit) memory cerebellum  putamen  caudate nucleus  motor cortex

Episodic and semantic memory

Declarative memory can be divided to: episodic memory semantic memory

Episodic memory Represents our memory of experiences and specific events in time in a serial form. It is the memory of autobiographical events.

Episodic memory Activity is concentrated in the hippocampus. Episodic memories are then stored in the neocortex. The memories of the different elements of a particular event (visual, olfactory, auditory areas) are all connected together by the hippocampus to form an episode.

Semantic memory More structured record of facts, meanings, concepts that we have acquired. It refers to general factual knowledge, independent of personal experience and of the spatial and temporal context in which it was acquired.

Semantic memory Much of semantic memory is abstract and relational and is associated with the meaning of verbal symbols. Semantic memory mainly activates the frontal and temporal cortexes.

Retrospective and prospective memory B) Retrospective and prospective memory

Retrospective memory The content to be remembered (people, words, events...) is in the past. Includes: semantic episodic autobiographical memory declarative memory (in general) can be implicit also

Prospective memory The content to be remembered is in the future. It may be defined as ˝remembering to remember˝ or remembering to perform an intended action. It may be event-based or time-based. It is often triggered by a cue. 

Literature http://www.human-memory.net http://neuroscience.uth.tmc.edu/s4/chapter07.html (John H. Byrne, Ph.D., Department of Neurobiology and Anatomy, The UT Medical School at Houston) Factmyth.com Brain-maps.com http://www.human-memory.net

Literature Squire LR, Wixted JT. The Cognitive Neuroscience of Human Memory Since H.M. Annual review of neuroscience. 2011;34:259-288. doi:10.1146/annurev-neuro-061010-113720.

Literature F.D.Raslau, I.T.Mark, A.P.Klein, J.L.Ulmer, V.Mathews, L.P.Mark. Memory Part 2: The Role of the Medial Temporal Lobe. American Journal of Neuroradiology. November 2014.